1. Field of the Invention
The present invention relates to heat exchange technology and, in particular, relates to an improved sealing component that may be used to reduce leakage between a hot gas conduit and a cold air conduit of a regenerative heat exchanging system.
2. Description of the Related Art
Conventional regenerative heat exchangers are used to provide preheated air to heavy machinery, such as a fuel burning power plant and may be used with various types of machinery that exhausts hot gas and operates more efficiently when supplied with preheated air, such as, for example, chemical processors, refineries, pulp and paper mills, and ships. Typically, two fluid stream passages extend through the heat exchanger. The first passage may include a hot gas conduit that communicates with a hot exhaust outlet of the power plant. Hot exhaust gases flow from the power plant exhaust into the hot gas conduit of the heat exchanger. The second passage may include a cold air conduit that communicates with a cool air intake passage of the power plant. Cold air conduit feeds pressurized air into the intake passage of the power plant. As is known in the art, regenerative heat exchangers extract heat from the exhaust gases of the fuel burning power plant and transfers the heat to the cool air conduit.
As is also known in the art, leakage between the hot gas conduit and the cold air conduit reduces the thermal efficiency of heat exchangers. It is therefore desirable to provide a sealing mechanism between hot and cold conduits so that gas does not leak between the hot gas conduit and the cold air conduit. Therefore, seals may be mounted at the junctions between the movable heat exchanging body and the housing of the heat exchanging apparatus. Unfortunately, conventional seals have many disadvantages. For example, seals are typically exposed to harsh operating conditions, such as erosive fly ash and soot. As the heat exchanging body moves with respect to the housing or vice versa, the seals are also exposed to mechanical abuse because the seals are positioned to maintain sliding contact with the sealing surfaces. Consequently, the seals wear down quickly.
Further, the high operating temperatures of the heat exchanging apparatus expose the seals to thermal stresses which often cause the seals to warp. The high operating temperature also causes thermal distortions in the shape of the structural members of the heat exchanging apparatus, such as the housing and center shaft. The distortions in the shape of the seals and the structural members affects the clearance between the seals and the sealing surfaces, often resulting in leakage paths between the hot gas conduit and the cold air conduit. This particular situation typically reduces the thermal efficiency of the heat exchanging apparatus and also reduces the overall efficiency of the system.
Conventional seal designs do not adequately address these problems. Some seals are made from relatively thick metal which holds up well against corrosion and mechanical abuse. However, such seals are not very flexible and often lose contact with the sealing surface when the structural members of the heat exchanging apparatus thermally distort. Other seals are extremely flexible so that they initially offer better sealing characteristics by expanding or contracting when the structural members thermally distort to maintain contact with the sealing surface. However, such seals hold up poorly to corrosion and mechanical abuse.
Certain prior art seals have been equipped with flexible portions that allow the seal to flex in response to deformations in the heat exchanger. For instance, U.S. Pat. No. 5,950,707 discloses a seal having resilient components that allow for flexible deformations. However, such seals may fracture or break when flexibly responding to torque stress loads that are produced by rotation of the heat exchanging body with respect to the outer housing of the heat exchanger. As a result, stress fractures may allow gas leakage between conduits.
Therefore, there exists a need for an improved resilient seal that may be used in conjunction with regenerative heat exchanging systems to reduce the adverse effects of rotational stress loads so as to substantially reduce the likelihood of leakage between hot and cold conduits. An improved resilient seal that resists corrosion abuse, mechanical abuse, and thermal distortion of the structural components would be preferred over conventional seals that are typically associated with regenerative heat exchanging systems and technology.
The aforementioned needs may be satisfied by the present invention, which relates to a seal assembly that is used to seal the angular sectors of a regenerative heat exchanging apparatus and prevent leakage between the hot gas conduit or exhaust conduit and the cold air conduit or intake conduit. The seal is advantageously configured to provide greater operating efficiency to a heat exchanging apparatus by ensuring positive contact between the heat exchanging body of a heat exchanger and the surfaces dividing the hot gas exhaust conduit and the cold air intake conduit and the sealing surfaces during relative movement therebetween even when exposed to harsh operating conditions and thermal distortion.
In one embodiment, a regenerative heat exchanging device comprises a plurality of radial and axial sector plates positioned so as to define an intake conduit and an exhaust conduit, wherein the intake conduit receives cool air so as to provide air to a power plant, and wherein the exhaust conduit receives heated gases that are exhausted from the power plant A rotor is attached to the plurality of radial and axial sector plates so as to rotate with respect thereto about an axis, wherein the rotor includes one or more heat absorbing sections that are alternatively rotated through the exhaust conduit and the intake conduit so that heat is absorbed in the exhaust conduit and is thereby transferred to the cool air in the intake conduit. The regenerative heat exchanging device has at least one seal having an outer edge, the at least one seal being mounted on an outer surface of the rotor so that the outer edge makes contact with an inner surface of the plurality of sector plates during rotation of the rotor so as to reduce the leakage of heat energy between the intake conduit and the exhaust conduit, wherein the at least one seal is deformable in a first direction that is opposite the direction of relative movement between the at least one seal and the inner surface in response to the outer edge of the at one seal making contact with the inner surface, and wherein the seal is simultaneously biased in a second direction opposite the first direction so that the outer edge of the at least one seal remains in contact with the inner surface over a range of distances between the rotor and the sector plate while the at least one seal rotates past the inner surface of the plurality of sector plates. A support member further reinforces the seal so as to inhibit damage to the seal during deformation of the seal in the first direction.
In another embodiment, a regenerative air preheater comprises an outer housing defining a first conduit and a second conduit, a heat exchanging body within the outer housing, the heat exchanging body configured to rotate with respect to the outer housing so that portions of the heat exchanging body are cyclically exposed to the first conduit and second conduit, and at least one seal located between the outer housing and the heat exchanging body, the seal including a mounting section connected to the heat exchanging body, a sealing section having a substantially straight outer edge that is contacting the outer housing, a means for resiliently and rotationally deflecting the seal in a direction opposite to a direction of rotation of the heat exchanging body so that the sealing section maintains contact with the outer housing over a range of distances between the heat exchanging body and the outer housing, and a means for reinforcing the seal in a manner so as to reduce over-flexing of the sealing section when the seal is deflected during rotation.
In yet another embodiment, a seal assembly for a regenerative preheater having a housing and a heat exchanging body that rotate with respect to each other in a first direction and define an interface therebetween comprises a seal member that is adapted to be interposed between the heat exchanging body and the housing so as to be positioned within the interface therebetween, wherein the seal member includes a deformable biasing section whereby the seal when in physical contact with at least a portion of both the housing and the heat exchanging body resiliently deforms in a second direction opposite the first direction of rotation between the housing and the heat exchanging body but is biased in the first direction, and a reinforcing member interposed between the housing and the heat exchanging body, wherein the reinforcing member is positioned with respect to the seal member so as to reinforce the seal member when the seal member is deformed in the first direction to thereby inhibit damage to the seal member as a result of the deformation.
These and other objects and advantages of the present invention will become more fully apparent from the following description taken in conjunction with the accompanying drawings. The illustrations are intended to illustrate, but not to limit, the invention.